a. Field
The instant disclosure relates to load modulated balanced amplifiers (LMBAs).
b. Background
In load modulated balanced amplifiers (LMBAs), RF power is combined from multiple individual power amplifiers (PAs)—two “main” PAs that comprise a balanced amplifier configuration, and one “control” PA. These PAs interact through a passive combining network such that the overall system output power is a function of the relative amplitude and phases of the multiple signals provided to the combining network. When an appropriate combining structure is used, the control PA interacts with the balanced amplifier PAs such that the load impedance seen by the main PAs is a function of variations in relative phase and amplitude of the control PA signal.
FIG. 1 shows an example load modulated balanced amplifier including two separate sources that generate a modulated RF input signal and a modulated RF control signal. Examples of this approach are described in D. Shepphard, J. Powell, S. Cripps, “An efficient broadband reconfigurable power amplifier using active load modulation.” IEEE Microwave and Wireless Components Letters, vol. 26, no. 6, June 2016 [Shepphard 1] and D. Shepphard, J. Powell, S. Cripps, “A broadband reconfigurable load modulated balanced amplifier (LMBA),” IEEE Int. Microwave Symposium, June 2017, pp. 1-3 [Shepphard 2]. In these approaches, however, the control signal is generated from an RF source that is separate from an input signal source, i.e., two sources are used. Balanced amplifiers use a related technique, but have no control signal injection.